Genetic mechanisms of pollution resistance in a marine invertebrate

Pollution is a common stress in the marine environment and one of today's most powerful agents of selection, yet we have little understanding of how anthropogenic toxicants influence mechanisms of adaptation in marine populations. Due to their life history strategies, marine invertebrates are unable to avoid stress and must adapt to variable environments. We examined the genetic basis of pollution resistance across multiple environments using the marine invertebrate, Styela plicata. Gametes were crossed in a quantitative genetic breeding design to enable partitioning of additive genetic variance across a concentration gradient of a common marine pollutant, copper. Hatching success was scored as a measure of stress resistance in copper concentrations of 0, 75, 150, and 350 mu g/L. There was a significant genotype 3 environment interaction in hatching success across copper concentrations. Further analysis using factor analytic modeling confirmed a significant dimension of across-environment genetic variation where the genetic basis of resistance to stress in the first three environments differed from that in the environment of highest copper concentration. A second genetic dimension further differentiated between the genetic basis of resistance to low and high stress environments. These results suggest that marine organisms use different genetic mechanisms to adapt to different levels of pollution and that the level of genetic variation to adapt to intense pollution stresses may be limited

improving mockup based requirement specification with end user annotations

Agile approaches, one of the key methodologies used in today's software projects, often rely on user interface mockups for capturing the goals that the system must satisfy. Mockups, as any other requirement artifact, may suffer from ambiguity and contradiction issues when several points of view are surveyed/elicited by different analysts. This article introduces a novel approach that enhances mockups with friendly end-user annotations that helps formalizing the requirements and reducing or identifying conflicts. We present an evaluation of the approach in order to measure how the use of annotations improves requirements quality

Adaptability of prolific varieties to plant density

International audienc

EARLY SUCROSE ACCUMULATION, A PROMISING CHARACTERISTIC TO USE IN SUGARCANE IMPROVEMENT PROGRAMS

Abstract IN MAURITIUS, sucrose content of cultivars harvested during the early part of the season is sub-optimal due to a shost ripening phase. Changes to the selection program and adoption of agronomic measures, such as artificial ripening, only partially solved the problem. The success recorded in other sugarcane industries on this aspect prompted basic studies. They were undertaken to understand the sucrose accun~ulation mechanism in parents, standasds, and seedling populations to redefine breeding and selection strategies for producing cultivars with substantially higher levels of sucrose for earlier harvest. Physiological and cane quality characters were assessed during the expoltential phase of growth at the age of seven months and at harvest early in the season at the age of eleven months. Statistically significant differences were recorded among parents and families, at the 99% level, for all characters irrespective of sampling date, and among standards, at the 95% level, in March only. Both significance level and variance were much higher during the growth phase. The best cane quality indicator, pol % cane diy matter, varied from 27.67% to 39.45% in,the growth phase and from 50.39% and 54.84% at harvest for the families. Categorisation of the parents according to their pol % cane dry matter in the exponential phase of growth was a better indicator of their sucrose accumulation pattern and maturity behaviour than their sucrose content on a fresh weight basis at harvest. Three distinct maturity groups, early, midlhigh sucrose and late were identified when considering sucrose accumulated during the growth phase. The early group accumulated more than 75% of its harvestable sucrose percent cane dly matter at the age of 7 months as opposed to about 55% in the late group. This is a clear indication of the genetic control for earliness, as environmental conditions were not conducive to sucrose accumulation. Proposals for improving breeding and selection for earliness are categorisation of all parents for their sucrose accuinulation pattern and mat~~rity behaviour to enable a better choice, screening during the growth phase on pol % dry matter, and the adoption of appropriate standards or increasing the selection pressure